Fixed handling too big values with \U on Jython.
Fixed handling too big values with \U on Jython.

Update issue 1524
Interestingly unichr raised TypeError with very large values on Jython when it raises OverflowError on Python. Changed the code to handle both.

userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3